1) For 500 chips, the best choice is likely a USPS priority medium flat rate box, $12.65 at the post office and $11.30 if you print the label online at USPS.com.
2) In addition, at 500 chips, the weight is probably just under 15lbs (at 11 grams a chip, 500 chips would be ~12lbs before packing materials), so it may cost less to ship via a USPS priority mail regional A box (max weight limit 15lbs). The rate goes by distance, but usually cost less than a medium flat rate box. The regional A box is smaller but should fit 500 chips.
The first option is the most straightforward, since the price is flat across the US and the weight limit is high (70lbs). Most people don’t have postal scales at home to accurately weigh their packages for option 2).